JPH03225603A - Switching circuit for recording and reproducing of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To simplify a peripheral structure by providing a DC supplying terminal for supplying a positive or negative voltage via a resistor to the bases of two transistors and switching the recording and reproducing of a magnetic head by controlling the on of either of the TRs to on and the other to off. CONSTITUTION:A reproducing amplifier 35 is put into an operating state and the TR 40 turns on and the TR 41 off when a DC voltage is supplied from the terminal 45. The current induced in the magnetic head 31 is, therefore, amplified in the reproducing amplifier 35 and is led out to an output terminal 39 via a rotary transformer 37, etc. The TR 40 turns off and the TR 41 on when a negative DC voltage is supplied to the terminal 45. Recording signals can then be supplied from a recording amplifier 36 to the magnetic head 31 via a rotary transformer 33. One piece of the slip ring for supplying the DC voltage to the terminal 45 is eventually necessitated for the slip ring required on the periphery of a rotary cylinder part in such a manner. The constitution around the rotary cylinder part is, therefore, simpler than heretofore.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) This invention relates to a magnetic recording and reproducing device (hereinafter referred to as V
The present invention relates to a recording/reproduction switching circuit used in a 3D (hereinafter referred to as TR).

(Prior Art) Digital VTRs and high-definition VTRs are required to be able to record and reproduce wider band signals than conventional analog VTRs. For this purpose, a method is adopted in which a bristle amplifier is built into the cylinder to improve the S/N of the recording/reproduction signal.

FIG. 2 shows a recording/reproducing circuit of a home high-definition VTR. Reference numeral 12 denotes a magnetic heald for recording and reproducing; a recording current is supplied via a transformer 13, and a reproducing current is derived via the transformer 13.

One terminal 131 of the transformer 13 is connected to the regenerative amplifier 14, and the other terminal 13□ is connected to the output terminal of the recording amplifier 15 and to the collector of the transistor 16. The emitter of this transistor 16 is grounded, and the base is connected to the reproduction power supply terminal 1 through a resistor R1.
7 is connected. This reproducing power supply terminal 17 is also connected to the power supply section of the regenerative amplifier 14. The output terminal of the regenerative amplifier 14 is connected to the input terminal of the rotary transformer 21. The output terminal of this rotary transformer 21 is led out as a reproduction signal output terminal 23.

On the other hand, a recording power supply terminal 18 is connected to the power supply section of the recording amplifier 15. This recording power supply terminal 18
is further connected to a terminal 131 of the transformer 13 via a diode 19.

A rotary transformer 2 is connected to the input terminal of the recording amplifier 15.
2 output terminal is connected to this rotary transformer 22.
The input terminal is used as the recording signal input terminal 24.

In the recording/reproduction switching circuit described above, the area surrounded by the broken line is the rotating portion of the rotating cylinder. Next, the operation will be explained. When the VTR is in playback mode, power is supplied to the terminal 17 via the slip ring. Then, the transistor 16 is turned on and the regenerative amplifier 14 becomes operational. The reproducing current induced in the magnetic head 12 is amplified by a reproducing amplifier 14 via a transformer 13, and is led out to an output terminal 23 via a rotary transformer 21.

Next, in the recording mode, power is supplied to the terminal 18 via the slip ring. Then, the recording amplifier 15 becomes operational, and the potential of one terminal 13 of the transistor 13 is set via the diode 19. Here, when a recording signal is supplied to the terminal 24, this signal is input to the recording amplifier 15 via the rotary transformer 22, amplified, and supplied to the transformer 13. This causes a recording current to flow through the magnetic head 12.

(Problems to be Solved by the Invention) According to the conventional recording/reproducing circuit described above, power supply switching is also necessary to switch between recording and reproduction, and two channels of slip rings are required for this purpose. For this,
There are problems such as the surroundings of the rotating cylinder becoming complicated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording/reproducing switching circuit for a magnetic recording/reproducing device that can reduce the number of channels for power supply, reduce the number of slip rings, and simplify the peripheral structure. .

[Structure of the Invention (Means for Solving the Problem) This invention provides an output terminal of a recording amplifier connected to one terminal of a coil of a magnetic head via a rotary transformer, and an output terminal of a recording amplifier connected to one terminal of a coil of a magnetic head. An input terminal of a regenerative amplifier is connected to the output terminal of the regenerative amplifier, and the output terminal of the regenerative amplifier is connected between the rotating cylinder section led out through a rotary transformer, one of the coils of the magnetic head, and the ground potential section.
and two NPN type and PNP type transistors connected between the other side of the coil and the ground potential part, respectively, and a positive or negative voltage is supplied to the bases of the two transistors via a resistor to connect either one of the transistors. and one DC supply terminal for controlling one of the magnetic heads to be on and the other to be off, thereby switching between recording and reproduction of the magnetic head.

(Function) With the above means, only one DC supply terminal and one slip ring are required. This allows the structure around the rotating cylinder portion to be configured simply.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. One terminal 31□ of the magnetic head 31 is connected to the output terminal of a recording amplifier 36 via a capacitor 32 and a daughter transformer 33, and is also connected to the collector of an NPN transistor 40. The emitter of this NPN transistor 40 is grounded. Also, the other terminal 3 of the magnetic head 31
12 is connected to the input terminal of the regenerative amplifier 35 via the capacitor 34, and is also connected to the collector of the PNP transistor 41. This PNP transistor 4
The collector of No. 1 is grounded.

A recording signal input terminal 38 is connected to the input terminal of the recording amplifier 36. Further, the output terminal of the regenerative amplifier 35 is connected to the input terminal of a rotary transformer 37, and the output terminal of this transformer 37 is connected to the reproduced signal output terminal 39.

Terminal 45 is a power supply and switching signal input terminal, and is connected to the base of transistor 40 via resistor 42 and to the base of transistor 41 via resistor 43. Furthermore, the terminal 45 is connected to the power supply terminal of the regenerative amplifier 35 via the diode 44.

This embodiment is constructed as described above. Now, when a positive DC voltage is supplied from the terminal 45, the regenerative amplifier 35 becomes operational. Further, the transistor 40 is turned on and the transistor 41 is turned off. Therefore, the current induced in the magnetic head 31 is amplified by the regenerative amplifier 35 and led out to the output terminal 39 via the rotary transformer 37.

Next, when a negative DC voltage is supplied to the terminal 45, the transistor 40 is turned off and the transistor 41 is turned on. Thereby, a recording signal can be supplied from the recording amplifier 36 to the magnetic head 31 via the rotary transformer 33.

As described above, according to this circuit, only one slip ring is required around the rotating cylinder portion for supplying DC voltage to the terminal 45. Therefore, the configuration around the rotating cylinder portion is simpler than that of the conventional one.

[Effects of the Invention] As explained above, according to the present invention, the number of channels for power supply can be reduced, the number of slip rings can be reduced, and the peripheral structure can be simplified.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional recording/reproduction switching circuit. 31...Magnetic head, 32.34...Capacitor,
3B, 37... rotary transformer, 35... reproducing amplifier, 36... recording amplifier, 40... NPN)
Transistor, 41...PNP transistor, 44...
··diode.

Claims (2)

[Claims] (1) The output terminal of a recording amplifier is connected to one terminal of the coil of the magnetic head via a rotary transformer, the input terminal of a regenerative amplifier is connected to the other terminal of the coil of the magnetic head, and the output terminal of the regenerative amplifier is connected to one terminal of the coil of the magnetic head. The terminals are NPN terminals connected to the rotating cylinder part led out through a rotary transformer, between one of the coils of the magnetic head and the ground potential part, and between the other coil and the ground potential part, respectively.
A positive or negative voltage is supplied to the bases of the two transistors through a resistor to control one of the transistors to be turned on and the other to be turned off, thereby recording data on the magnetic head. , and one DC supply terminal for switching reproduction. (2) The recording/reproducing switching circuit for a magnetic recording/reproducing apparatus according to claim 1, wherein the positive voltage is supplied during reproduction and also serves as a power source for the reproducing amplifier.